The prior art related to the extraction of samples of granular or particulate materials, such as wood chips, includes a number of United States Patents, included among which are the following:
U.S. Pat. No. 2,495,944 issued to W. H. Pletta et al shows a coal sampler in which a sample collector is formed of a length of pipe which has a longitudinally extending quarter section removed to provide an arcuate opening. The sample collector is pivotally mounted so that it can be swung from one side of a falling coal stream to the other and back again. While the sample collector is in the stream the sample collector rotates in order to catch a sample of the coal stream. When the sample collector leaves the falling stream, the sample collector rotates to discharge the sample.
U.S. Pat. No. 2,683,373 issued to R. W. Gallup et al shows a grain sampler in which a sample cup is inserted into a stream of falling grain. As the cup is inserted into the stream, its motion is guided by a keyway to turn 180 degrees to face upward to be filled. The cup then retracts, still facing up until it reaches almost the end of its retraction stroke, whereupon it rotates 180 degrees to dump the grain.
U.S. Pat. No. 3,782,200 issued to Maas shows a sampling tube which is transversely mounted in a conveying pipe. Falling material enters the sample tube through an inlet opening. A plunger pulls the material in the sampling tube allowing it to fall through a discharge opening.
U.S. Pat. No. 4,743,155 issued to Carey et al shows an inclined conveyor which includes a chain with a plurality of flights which catch a portion of a falling stream and carry it to a sampling bin.
U.S. Pat. No. 4,574,645 issued to Allen et al shows an inclined tube which is permanently located in a vertical chute. The end of the tube has an opening which allows chip samples to enter the tube. When chip samples are to be taken, the tube is rotated 180 degrees in order to align the opening in the tube with the stream of chips, thereby allowing chips to enter the tube and pass downwardly into a container.
U.S. Pat. No. 4,625,570 issued to Witherspoon et al shows a scoop which fills when a cradle faces upwardly into a flow of material. After retraction of the scoop out of the stream of material, the scoop rotates to dump the sampled material.
Each of the devices described in the above patents is generally complex in construction and is not capable of automatically extracting repeatable and representative samples of wood chips. Thus, despite the various types of devices described in the above patents, the need for a practical wood chip sampler has not been met by the prior art.